I know that if I started fasting, and then my period starts during Asr, or some other time during the day, my fast becomes invalid. So should I break my fast or continue to not eat throughout the day?
بسم الله الرحمن الرحيم
(Fatwa: 1309/901/L=11/1434)
The fast breaks when the menses starts. It is lawful for you to eat and drink after it. It is not necessary to remain without food the whole day.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband